Flotation of arsenic minerals from borate ores

ABSTRACT

Arsenic minerals, such as realgar, may be removed by flotation from hot slurries of borate ores, such as ulexite, colemanite and tincal with or without the aid of a flotation reagent.

ilnited States Patent Sawyer et al.

[ Get. 30, 1973 FLOTATION OF ARSENIC MINERALS FROM BORATE ORES lnventors: Dwight L. Sawyer, Boron; Martin Wilson, Anaheim, both of Calif.

Assignee: United States Borox & Chemical Corporation, Los Angeles, Calif.

Filed: Oct. 21, 1971 Appl. No.: 191,536

References Cited UNITED STATES PATENTS 11/1906 Sulman 209/166 1,208,334 12/1916 Lavers 209/166 2,184,558 12/1939 Malozemoff.. 209/166 X 2,257,710 9/1941 Archibald 209/166 2,317,413 4/1943 Shelton 209/166 2,741,364 4/1956 Wilson 209/166 X FOREIGN PATENTS OR APPLlCATlONS 100,223 11/1940 Sweden 209/166 602,686 12/1925 France 209/166 749,467 5/1944 Germany 209/166 1,137,115 1/1957 France 209/166 Primary Examiner-Robert Halper AttorneyJames R. Thornton [57] ABSTRACT Arsenic minerals, such as realgar, may be removed by flotation from hot slurries of borate ores, such as ulexite, colemanite and tincal with or without the aid of a flotation reagent.

10 Claims, No Drawings FLQTATHON OE ARSENTC MINERALS FROM BQRATE ORES In accordance with the precepts of the invention, realgar, As.,S or AS 5 the predominant arsenic mineral in soluble borax ore, such as tincal, is removed by flotation of a hot approximately saturated slurry, preferably at least 75 C., although such removal cannot easily be obtained if the slurry is at room temperature. A pH adjustment is not required because flotation occurs readily at the natural pH of about 9.2. The process may be carried out without the use of a flotation reagent, although if desired, one may be used to enhance the ease of flotation. This process makes it possible to remove between about 80 percent to 98 percent of the contained arsenic by means of a flotation process, wherein oftentimes only a single step may be necessary. This is unexpected in view of the slime forming clay content of such ore. Flotation of realgar in saturated borax solutions at room temperature is sluggish and incomplete.

Similarly, it has been found that the same flotation technique may be applied with other borate ores, such as ulexite and colemanite. Ulexite is a natural hydrated borate of sodium and calcium, NaCaB O 8H O. Colemenite is a natural hydrated calcium borate Ca B- O '5l-l O. However, the solubility of these ores are considerably less in water than tincal.

It has also been discovered that when applying the method of the present invention to a borax containing ore such a tincal, the considerable amount of strong borax liquor present in the floated realgar may be recovered to make the process more economical. Filtration of the concentrate is difficult because of the clay slimes present. The desired further recovery may be accomplished by refloating the concentrate after dilution with weak liquor. The cleaner concentrate slurry, containing mainly weak liquor, may be discarded and the cleaner tailings slurry is returned to the ore dissolver.

In carrying out the invention, the ore slurry is prepared by crushing the ore to at least minus 20 mesh preferably minus 50 mesh and then heating with water, or by heating the coarse ore with water and passing the solution through a 50 mesh screen.

Commercial flotation cells may be used as rougher cells and as cleaner cells. For relatively small scale operations, the well known Denver Lab cells, manufactured by Denver Equipment Company, were employed in the examples set forth below. The cells may be operated in series to improve the efficiency of the process.

10 used in the manner well known in the art.

The water insolubles in the rougher tailings slurry are flocculated. After settling in a thickener, the hot overflow brines are sent to a crystallizer.

, EXAMPLES l-VI An approximately saturated borax slurry was prepared by crushing 150 g. of soluble tincal to minus 50 mesh, slurrying with 250 ml. of water, and heating the mixture to 95 to 100 C. When flotation agents were employed, as in Examples l-V, they were added to the hot slurry. After thirty seconds conditioning, the slurry (at 95 C.) was tranferred to a 100 g. Denver Lab cell where air froth flotation was maintained for 2.5 minutes. The test data are set forth in the following Table TABLE I Arsenic distri- Tincal ore Flotation reagent butlon, percent Insoluble, Conper- AS203, cen- Examplc cent p.p.m. Kind Lb./ton trate Tails 3 8, 200 Ethylxanthateu 0.5 98.2 1.8 14 3,800 do 0.25 86.9 13.1 14 3,800 d0..-. 0 125 89.2 10.8 20 1,700 Kerosene. 0.5 79.8 20.2 14 3,800 do 0 25 86.9 13.1 14 3,800 None 85.8 14.2

EXAMPLES Vll-lX Examples Vll-lX show the influence of water insolubles and orpiment (AS253) on the process. The ore used for Example IX contained some orpiment and turned yellow during crushing. The ore for Example Vll was crushed to minus 20 mesh while those for Examples VI! and IX were crushed to minus mesh. Except as In the Denver cell, the slurry flows into the machine by gravity through the feed pipe, dropping the slurry directly on the top of the rotating impeller below a stationary hood. This is the mixing and aeration zone where air is drawn in by positive suction down a standpipe into the heart of the cell. Zone 2 is the separation zone where the arsenic-laden air bubbles separate from the borate solution or slurry. Zone 3 is the concentrate EXAMPLES X XlV The special influence of flotation reagents is illustrated by Examples X-XIV. The ore contained about 14% water-insolubles and about 3,800 ppm. AS203. The slurry particles were less than 20 mesh and were processed as before.

TABLE III Cncen Example Kind Lb/T on trate Tails X Ethylxanthate 0.5 88.3% 11.7% X1 0.25 88.9 13.1 XII 0.125 89.2 10.8 XIII None 85.8 14.2 XIV Kerosene 0.25 86.9 13.1

It will be seen from the above that more arsenic is floated from the cell when a flotation agent is employed.

EXAMPLES XV XVII In each of the following examples, a 100 g. Denver flotation cell was charged with 50 g. of minus 100 mesh ulexite ore which was slurried with 40 ml. of water. The temperature of the slurry was as indicated in Table IV. The pH was 9.0 when cold and 9.2 when hot. Additional water was added, hot in the case of XV and XVI examples. Air was introduced to produce a good froth. Each flotation step, in conjunction with each example, was run 9.0 2.5 minutes.

The first flotation gave a first tail and an arsenic concentrate. The concentrate was refloated to give a second tail and the final concentrate. ln examples XV and XVII, no flotation reagents were included while in example XVI, two drops of kerosene was included. The temperature during the flotation steps was as indicated in Table IV.

It will be seen that arsenic recovery is higher in the final concentrate when a flotation reagent is employed. In example XVII, the arsenic recovery in the final concentrate is only 67.3 percent of the total. However, it will be also seen that the temperature of the slurry during the flotation steps was only between 27 to 33 (3., clearly demonstrating that the higher temperatures produce admirably better results.

TABLE IV Starting Ore Ulexite Containing 4080 ppm. As Example XV Flotation Reagent None Temperature (C.) Start Finish First Flotation 90 84 Second Flotation 93 85 Wt. AS Total (1;) (PP AS First Tail 31.4 26 0.4

Second Tail 5.9 1520 4.3

Final Concentrate 2.6 76800 95.3

Total 39.9

Example XVI Flotation Reagent Kerosene (2 drops) Temperature (C.) Start Finish First Flotation 92 86 Second Flotation 95 80 Wt. As Total (8) (pp AS First Tall 33.2 80 1.3

Second Tail 5.2 68 .2

Final Concentrate 2.5 80,000 98.5

Total 40.9

Example XVII Flotation Reagent None Temperature (C.) Start Finish First Flotation 27 30 Second Flotation 29 33 5 of Wt As Cone. Total (g) (Pa As First Tail 28.1 1080 19.1 Second Tail 9.3 2320 13.6 Final Concentrate 4.9 21800 67.3

Total 42.3

As stated in the above, when operating with a soluble ore such as tincal there is considerable loss of soluble borate in the first or rough concentrate. While the examples in the above pertaining to ulexite incorporate a second flotation, the same procedure is suggested with regard to tincal in order to recover the soluble borate which may be lost in the rougher concentrate.

Although the examples described in the above were carried out in a Denver Lab cell having a capacity of 100 ml., in commercial operation cells having a capacity of 2 to 100 cubic feet, preferably from 40 to 100 cubic feet, would be used. These larger cells will give a lower strong borax retention in the rougher concentrate and a lower arsenic transfer to the cleaner tailings, thereby improving the efficiency of the process.

It will be apparent that many changes and modifications may be made in the process descirbed herein without departing from the spirit and scope of the invention. It is therefore apparent that the foregoing description of by way of illustration of the invention and not by way of limitation.

What is claimed is:

l. The method of removing arsenic sulfide minerals from hydrated sodium and calcium borate containing ores comprising the steps of forming an aqueous slurry of said ore at a temperature of from about 75 to about 100 C., and subjecting said hot slurry to froth flotation and then separating the tailings from the floated materials which will contain a concentrate of said minerals.

2. The method of claim 1 wherein said slurry is conditioned with a flotation reagent selected from the group consisting of alkyl xanthates having two to five carbon atoms, kerosene, diesel oil and bunker oil prior to the flotation step.

3. The method of claim I wherein the mineral is realgar.

4. The method of claim 1 wherein the ore is tincal.

5. The method of claim I wherein the ore is ulexite.

6. The method of claim 11 wherein the ore is colemanite.

7. The method of claim I wherein the process is conducted at the natural pH of the ore of about 9.

8. The method of claim 1 wherein said ore is crushed to at least minus mesh prior to forming said aqueous slurry.

9. The method of claim I wherein said ore is crushed to at least minus 50 mesh prior to forming said aqueous slurry.

10. The method of claim 11 wherein said aqueous slurry is passed through a 50 mesh screen prior to froth flotation. 60 =i= =1:

Patent No. 3,7 ,73 Dated October 3 973 Inventor(s) Dwight L. Sawyer and Martin Wilson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 2, line 3 delete KIrk" and add "Kirk";

In Column 2, line M delete "VII" and add --VIII--;

In Column 2, TABLE II under the heading "Tails',' line 57 add -percent--,'

In Column 2, line 58 delete and add --l.8--;

line 59 delete and add --20.2--,' line 60 delete and add --l7.'T-,'

In Column 3, line 22 delete "9.0" and add --for--.

Signed and sealed this 16th day of April 1971 (SEAL Atte st:

EDLJ I'LFLETCHERJR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM FO-105O (10-69) USCOMM'DC 60376-5 69 Q U. S GOVFRNMIN'I' PRINTING OFFICE IIII 0-8l-3Sl, 

2. The method of claim 1 wherein said slurry is conditioned with a flotation reagent selected from the group consisting of alkyl xanthates having two to five carbon atoms, kerosene, diesel oil and bunker oil prior to the flotation step.
 3. The method of claim 1 wherein the mineral is realgar.
 4. The method of claim 1 wherein the ore is tincal.
 5. The method of claim 1 wherein the ore is ulexite.
 6. The method of claim 1 wherein the ore is colemanite.
 7. The method of claim 1 wherein the process is conducted at the natural pH of the ore of about
 9. 8. The method of claim 1 wherein said ore is crushed to at least minus 20 mesh prioR to forming said aqueous slurry.
 9. The method of claim 1 wherein said ore is crushed to at least minus 50 mesh prior to forming said aqueous slurry.
 10. The method of claim 1 wherein said aqueous slurry is passed through a 50 mesh screen prior to froth flotation. 